1. Field of the Invention
The invention is in the field of ion optics.
2. Description of Related Art
Ion guides comprising four electrodes are used to transport ions from one place to another. For example, in mass spectrometry ion guides may be used to transport ions from an ion source to an ion analyzer. Some types of ion guides operate using radio frequency potentials applied to the four electrodes. Neighboring electrodes (orthogonal to each other) in the ion guide are operated at potentials of opposite polarity, while opposing electrodes in the ion guide are operated at the same potentials. The use of appropriate potentials results in the generation of a quadrupole field and an ion channel through which ions will preferentially travel. In some instances, such ion guides also operate as a mass filter or collision cell.